Both MIT and Heimdal are unable to, in krb5_cc_default(), call to KCM
(or CCAPI, or LSA, or...) to get the user's default ccache name in their
collection. Instead, the default ccache name is obtained in a static
way, and for KCM that's "%{UID}". When we krb5_cc_switch(), we simply
maintain a pointer to the name of the ccache that was made the default,
but klist can't make use of this because krb5_cc_default() can't.
The solution here is to first try resolving the ccache name given by the
client, and if that fails but the name happens to be what would be the
library's default KCM ccache name for that user, then try resolving it
through the default ccache name pointer saved at switch time.
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